Font lost for characters with accent

I read a french rtf file which has a Verdana font, modify a few run and save it to doc format.
All characters with accent show now in “Times new Roman” instead of “Verdana”.
I cannot even search and replace the font (it is not found) and when I insert a new character whith accent, its font is “Times new Roman”.
Can any one help ?
thank you

Thanks for your request. Could you please attach your document for testing and provide me your code? I will investigate this problem and provide you more information.
Best regards.